Optical imaging techniques for hypersonic impulse facilities

2007 ◽  
Vol 111 (1115) ◽  
pp. 1-16 ◽  
Author(s):  
T. J. McIntyre ◽  
H. Kleine ◽  
A. F. P. Houwing
Keyword(s):  
Optical Imaging ◽  
High Speed ◽  
Imaging Techniques ◽  
Flow Visualisation ◽  
Complex Flows ◽  
High Speed Imaging ◽  
Time Resolved ◽  
Flow Parameters ◽  
Planar Laser ◽  
Recent Developments

Abstract The application of optical imaging techniques to hypersonic facilities is discussed and examples of experimental measurements are provided. Traditional Schlieren and shadowgraph techniques still remain as inexpensive and easy to use flow visualisation techniques. With the advent of faster cameras, these methods are becoming increasingly important for time-resolved high-speed imaging. Interferometry’s quantitative nature is regularly used to obtain density information about hypersonic flows. Recent developments have seen an extension of the types of flows that can be imaged and the measurement of other flow parameters such as ionisation level. Planar laser induced fluorescence has been used to visualise complex flows and to measure such quantities as temperature and velocity. Future directions for optical imaging are discussed.

High Speed Imaging Techniques For Pulse Nuclear Radiation Source

1989 ◽  
Author(s):  
Wang Kuilu ◽  
Lu Ming ◽  
Liu Cunfu ◽  
Kang Dechun
Keyword(s):  
Radiation Source ◽  
High Speed ◽  
Imaging Techniques ◽  
Nuclear Radiation ◽  
High Speed Imaging

High Speed Imaging of Forced Ignition Kernels in Non-Uniform Jet Fuel/Air Mixtures

2017 ◽  
Author(s):  
Sheng Wei ◽  
Brandon Sforzo ◽  
Jerry Seitzman
Keyword(s):  
Heat Release ◽  
High Speed ◽  
Air Flow ◽  
Cetane Number ◽  
High Energy ◽  
Liquid Fuels ◽  
High Speed Imaging ◽  
Ignition Probability ◽  
Turbine Engine ◽  
Planar Laser

This paper describes experimental measurements of forced ignition of prevaporized liquid fuels in a well-controlled facility that incorporates non-uniform flow conditions similar to those of gas turbine engine combustors. The goal here is to elucidate the processes by which the initially unfueled kernel evolves into a self-sustained flame. Three fuels are examined: a conventional Jet-A and two synthesized fuels that are used to explore fuel composition effects. A commercial, high-energy recessed cavity discharge igniter located at the test section wall ejects kernels at 15 Hz into a preheated, striated crossflow. Next to the igniter wall is an unfueled air flow; above this is a premixed, prevaporized, fuel-air flow, with a matched velocity and an equivalence ratio near 0.75. The fuels are prevaporized in order to isolate chemical effects. Differences in early ignition kernel development are explored using three, synchronized, high-speed imaging diagnostics: schlieren, emission/chemiluminescence, and OH planar laser-induced fluorescence (PLIF). The schlieren images reveal rapid entrainment of crossflow fluid into the kernel. The PLIF and emission images suggest chemical reactions between the hot kernel and the entrained fuel-air mixture start within tens of microseconds after the kernel begins entraining fuel, with some heat release possibly occurring. Initially, dilution cooling of the kernel appears to outweigh whatever heat release occurs; so whether the kernel leads to successful ignition or not, the reaction rate and the spatial extent of the reacting region decrease significantly with time. During a successful ignition event, small regions of the reacting kernel survive this dilution and are able to transition into a self-sustained flame after ∼1–2 ms. The low aromatic/low cetane number fuel, which also has the lowest ignition probability, takes much longer for the reaction zone to grow after the initial decay. The high aromatic, more easily ignited fuel, shows the largest reaction region at early times.

Special high speed imaging techniques using phase, aperture, and polarization effects

2013 ◽  
Author(s):  
Wenjing Zhao ◽  
Daniel C. Skaloud ◽  
Sascha Kutz ◽  
Hendrik Rothe ◽  
Cornelius F. Hahlweg
Keyword(s):  
High Speed ◽  
Imaging Techniques ◽  
High Speed Imaging ◽  
Polarization Effects

scholarly journals High-Speed Imaging of Forced Ignition Kernels in Nonuniform Jet Fuel/Air Mixtures

2018 ◽  
Vol 140 (7) ◽  
Author(s):  
Sheng Wei ◽  
Brandon Sforzo ◽  
Jerry Seitzman
Keyword(s):  
Heat Release ◽  
High Speed ◽  
Air Flow ◽  
Cetane Number ◽  
High Energy ◽  
Liquid Fuels ◽  
High Speed Imaging ◽  
Ignition Probability ◽  
Turbine Engine ◽  
Planar Laser

This paper describes experimental measurements of forced ignition of prevaporized liquid fuels in a well-controlled facility that incorporates nonuniform flow conditions similar to those of gas turbine engine combustors. The goal here is to elucidate the processes by which the initially unfueled kernel evolves into a self-sustained flame. Three fuels are examined: a conventional Jet-A and two synthesized fuels that are used to explore fuel composition effects. A commercial, high-energy recessed cavity discharge igniter located at the test section wall ejects kernels at 15 Hz into a preheated, striated crossflow. Next to the igniter wall is an unfueled air flow; above this is a premixed, prevaporized, fuel–air flow, with a matched velocity and an equivalence ratio near 0.75. The fuels are prevaporized in order to isolate chemical effects. Differences in early ignition kernel development are explored using three synchronized, high-speed imaging diagnostics: schlieren, emission/chemiluminescence, and OH planar laser-induced fluorescence (PLIF). The schlieren images reveal rapid entrainment of crossflow fluid into the kernel. The PLIF and emission images suggest chemical reactions between the hot kernel and the entrained fuel–air mixture start within tens of microseconds after the kernel begins entraining fuel, with some heat release possibly occurring. Initially, dilution cooling of the kernel appears to outweigh whatever heat release occurs; so whether the kernel leads to successful ignition or not, the reaction rate and the spatial extent of the reacting region decrease significantly with time. During a successful ignition event, small regions of the reacting kernel survive this dilution and are able to transition into a self-sustained flame after ∼1–2 ms. The low-aromatic/low-cetane-number fuel, which also has the lowest ignition probability, takes much longer for the reaction zone to grow after the initial decay. The high-aromatic, more easily ignited fuel, shows the largest reaction region at early times.

High‐speed imaging techniques for harpsichord plucking action.

2010 ◽  
Vol 127 (3) ◽  
pp. 1733-1733
Author(s):  
Marshall J. Brown ◽  
C.‐Y. Jack Perng ◽  
Thomas D. Rossing ◽  
Juliette W. Ioup
Keyword(s):  
High Speed ◽  
Imaging Techniques ◽  
High Speed Imaging

Electrically tunable lenses – eliminating mechanical axial movements during high-speed 3D live imaging

2021 ◽  
Vol 134 (16) ◽  
Author(s):  
Christoforos Efstathiou ◽  
Viji M. Draviam
Keyword(s):  
Cell Biology ◽  
High Speed ◽  
Imaging Techniques ◽  
Three Dimensional ◽  
Cost Effective ◽  
High Speed Imaging ◽  
Liquid Lenses ◽  
Live Cell Microscopy ◽  
Tunable Lenses ◽  
Cell Microscopy

ABSTRACT The successful investigation of photosensitive and dynamic biological events, such as those in a proliferating tissue or a dividing cell, requires non-intervening high-speed imaging techniques. Electrically tunable lenses (ETLs) are liquid lenses possessing shape-changing capabilities that enable rapid axial shifts of the focal plane, in turn achieving acquisition speeds within the millisecond regime. These human-eye-inspired liquid lenses can enable fast focusing and have been applied in a variety of cell biology studies. Here, we review the history, opportunities and challenges underpinning the use of cost-effective high-speed ETLs. Although other, more expensive solutions for three-dimensional imaging in the millisecond regime are available, ETLs continue to be a powerful, yet inexpensive, contender for live-cell microscopy.

Investigation of Auto-Ignition of a Pulsed Methane Jet in Vitiated Air Using High-Speed Imaging Techniques

2010 ◽  
Vol 133 (2) ◽  
Author(s):  
W. Meier ◽  
I. Boxx ◽  
C. Arndt ◽  
M. Gamba ◽  
N. Clemens
Keyword(s):  
High Speed ◽  
Gas Flow ◽  
Imaging Techniques ◽  
Frame Rate ◽  
Experimental Arrangement ◽  
Single Shot ◽  
Exhaust Gas ◽  
High Speed Imaging ◽  
Auto Ignition ◽  
Flow Field Characteristics

An experimental arrangement for the investigation of auto-ignition of a pulsed CH4 jet in a coflow of hot exhaust gas from a laminar lean premixed H2/air flame at atmospheric pressure is presented. The ignition events were captured by high-speed imaging of the OH∗ chemiluminescence associated with the igniting flame kernels at a frame rate of 5 kHz. The flow-field characteristics were determined by high-speed particle image velocimetry and Schlieren images. Furthermore, high-speed imaging of laser-induced fluorescence of OH was applied to visualize the exhaust gas flow and the ignition events. Auto-ignition was observed to occur at the periphery of the CH4 jet with high reproducibility in different runs concerning time and location. In each measurement run, several hundred consecutive single shot images were recorded from which sample images are presented. The main goals of the study are the presentation of the experimental arrangement and the high-speed measuring systems and a characterization of the auto-ignition events occurring in this system.

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